Ellipsograph



Feb. 4,1947. l Q J, HQBSON 2,4152833 ELLIPSOGRAPH Filed April 17, 1944INVEN'TOR .0L/VER d Hasso/v ms ATTORNEY Patented Feb. 4, 1947 UNITEDySTATES PATENT OFFICE.Y

ELLIPSOGRAPH" (Hiver J. Hobson, Redwood City, Calif.

ApplicationApi-il 17, 1944, Serial No.-531,371'

l Myinventicn relates Vto instruments `^for draw-` ing ellipses; andtheprincipalobject of my invention is the provision of an instrumentwith" ment; and also 'an instrument in which adjustments arereadilymade'V to draw ellipses having specific major and minordiameters.

M 1 invention possesses other objects land features of value, some ofwhich vwith the foregoing will be set forth in the followingVdescription of the invention. It i'sto be understood that I do notlimit myself `to the `shovvingmaole by the said description and thedrawing as I may adopt variant forms of the inventionfwithin the scopeof the appended claims;

.teferring to the drawing:

Figure Il a plan View of one embodiment of my invention; and Figure 2 isa front elevation partly in section, of the supporting base fand rollingcarriage only. TheA plane of section is indicated by the line2-`2 ofFigure l.

Figure 3 is a detail in Vertical central section and cn an enlargedscale of the pivotal slide Figure iis a side elevation, on an enlargedscale of the rotaryhead of the instrument.

In terms of broad inclusion the curve generating device of my inventionas shown by Figures l to 4 inclusive, comprises pantograph arms somounted ccntrolledthat the scribng point moves in full scale in onedirection, but in a selected proportional scale in a-direction alt rightangles to the full scale direction; modified pantcgraplireduction isapplied to a circle, a symmetrical closed curve may be traced which inits long diameter `is the diameter of the circle, but in its shortdiameter bears a predete, mined ratio to the `circle diameter.

The curve iullls the technical definition of a true ellipse and quitesatisfactorily supplies the curves required in perspective .views ofcircular or cylindrical objects.

The instrument shown in Figure 1 comprises a carrier orcarriage-Whichlismnunted on a 'track tc move backl andewforthover aiplaten or table on which 'paper 4whichis-.toV receive thegure laid, A.crank of adjustable throw is arranged to turn about a bearing` fixed inthe table; and is so connected to the carrier that the carriage Vfhe'nthis f A is reciprocatedon thetrack; A pair-of links,Uv

pivoted together `at their ends,` is mounted' with the free end 'of onelink journaledron the Ycrank andthe free'end of theother link pivoted onthe carriage. A secondf pairof pivoted `linksis adjustably and pivotallyconnected' to the iirst pair in the shape cf` a parallelograin; and tliescrilo` ing point is preferably supported in the axis `of the pivotalconnection of thesecondpair of links. The proportions `andarrangementofpartsis such that the scribin'g`` point lies in a line connesting theaxes `of the crank andpivotal con# nection' of the first "pairof linksto the 'carriage.` When these 'conditions'arefulfilled'the' scriber4traces a true" ellipse. fWithlio'ther setting'a'or' with the scribercarried; Yforexample-on. 'one of the 'links intermediatetherends;other-curves would be traced," Vlout these-are' not part of the'presently intended-use of the 'instrument-' and the possibilities inthis directionneed'not be here 1 explored;

A carriage'cr ca'rrier 2 isfl provided with `wheels 3 designedto run'inthetrackwaysformed in the upperffaoe'of the vtablecr platen 6. T"Thisallows the 'tableto move'back and forth', .each` point on it travelingin astraightline." A pivot join l' is ilXed adjacentonecorner 'of thecarrier,` which` is cut away 'as showniin Figure "l to provide a WorkingIspace for the scribing point 'In the opposite `side of the carrier andin line with the pivot pin l, is atslot '8, in Which-the crank pin il isarranged to move hackl and forthas the 1 crank arm l i' turns about its4pivotal'mounting stud i2.

The stud extends downwardly from the ilat base i5 provided to givestability to the 'crank arm` and is journaled in the bearing `hole lliin the platen. Extending'upvvardly fromthe base'l is clamping theblockin aiselected position on the `crank arm to vary the 'throw' ofthel crank pin, and graduations 2s on theV crank arm facilitate thissetting; providing guidance in the' selection of the major diameter oftheproposed ellipse 2l. it willl be understood of course that with lthecrank 'pin' engaged in the slot the carrier is mcvedfzcaek and forthbythe turning o'f the crank; a distance" equal vto twicethe `throw ofthelcrank loin.

Means are prcvidedr-for connecting` the 'pivot pin l which moves backand forth with the oarrier in a straight line, to the crank pin 9 whichmoves around in a circle, and for supporting a scriber on the connectingmeans. A pair of links 22 and 23, connected together at one of theirends by the pivot 24, are connected at their other ends to the pivot pin1 and crank pin 9; and carried by these links are two other links 26 and21 connected at one of their ends by the pivot 28 in which a scriber 29is held. lConveniently the connection may be a simple grommet of a sizeto hold frictionally the scribing point.

The second pair of links are connected to the first pair to form aparallelogram with the point of the scriber in the line connecting thecenter of pivot pin 'I and the longitudinal center line of the groove 8.The connecting device is shown in Figure 3 and each comprises a pair oflike spring clips 3| pivoted together by the pin 32, and having springarms 33 resiliently engaging around the body of the link. A pointed tab34 e centrally placed on one side provides a convenient indicator forplacing the center of the pivot pin 32 at any desired setting relativeto the graduations 36 on the links. These graduations are preferablyplaced on both sides of links 22 and 21; and for accurate setting, thelink assembly is preferably lifted off of the pins 1 and 9, so that theindicator points of the tabs 34 can be brought into close register withthe graduations, which are calculated to provide guidance relative tothe minor axis of the proposed ellipse 2 I.

Operation-The major aXis of the proposed ellipse is the same as twicethe throw ofthe crank pin 9; that is, the same as the diameter of thecircle generated by the center of the crank pin. The block I8 istherefore adjusted on the crank arm to give the desired throw. Thegraduations 20 may be in inches, centimeters, or an arbitrary unit asdesired. The links are then adjusted to form a parallelogram with thescriber l point aligned with the slot 8 as above explained. While it ismechanically impossible in this embodiment of my invention to coincidethe scriber point with the axis of either the pivot pin 'I or the crankpin 9, such positions theoretically fix the minimum and maximum valuesof the minor axis of the ellipse generated, that is from zero value tothe length of the major axis. The nearer the pivotal connections betweenthe links to the pivots 1 and 24, the flatter the ellipse. Moving thepivotal connections toward the pivots 24 and 9 lengthens the minor axis.Here too the graduations may be in any desired units best fitted toextend usefulness and facility in handling.

After setting the instrument, the paper on which the ellipse is to bedrawn is placed in position under the scriber, and held securely whilethe crank pin ismanually rotated through one revolution.

I claim:

1. A device for drawing ellipses comprising a carrier, track means onwhich the carrier :may move back and forth, a xed bearing, a crank pinmounted for turning about the bearing, means connecting the crank pinwith the carrier to reciprocate the carrier when the crank is turned, apair of links pivoted together, the vfree end of one of the links beingjournaled on the crank pin and the free end of the other link beingpivoted to the carrier, and a second pair of links pivoted together andto the first pair at points intermediate the ends of the latter to formtherewith a parallelogram, and means onthe secon pair of links forholding a scriber.

2. A device for drawing ellipses comprising a carrier, track meansonwhich the carrier may move back and, forth, a fixed bearing, a crank pinmounted for turning about the bearing, means connecting the crank pinwith the carrier to'reciprocate the carrier when the crank is turned, apair of links pivoted together, the free end of one of the links beingjournaled on the crank pin and the free end of the other link beingpivoted to the carrier, a second pair of links pivoted together andpivoted to the rst pair to form therewith a parallelogram, and means atthe pivotal connection of the second pair of links for holding ascriber.

3. A device for drawing ellipses comprising a carrier, track means onwhich the carrier may move back and forth, a fixed bearing, a crank pinmounted for turning about the bearing, a slot in the carrier at rightangles to the line of its movement on the track means and in which thecrank pin may reciprocate to reciprocate the carrier when the crank isturned, a pair of equal links pivoted together, the free end of one ofthe links being pivoted on the crank pin and the free end of the otherlink being pivoted to the carrier at a point in alignment with thelongitudinal axis of said slot, a second pair of links pivoted togetherand pivoted to the lst pair at points intermediate the ends of thelatter to form therewith a parallelogram, and means on the second pairof links for holding a scriber.

4. A device for drawing ellipses comprising a carrier, track means onwhich the carrier may move back and forth, a Xed bearing, a crank pinmounted for turning about the bearing, a slot in the carrier at rightangles to the line of its movement on the track means and in which thecrank pin may reciprocate to reciprocate the carrier when the crank isturned, a pair of equal links pivoted together, the free end of one ofthe links being pivoted on the crank pin and the free end of the otherlink being pivoted to the carrier at a po'int in alignment with thelongitudinal axis of said slot, a second pair of links pivoted togetherand pivoted to the first pair at points intermediate the ends of thelatter to form therewith a parallelogram, and means on the second pairof links for holding a scriber in alignment with the said longitudinalaxis of the slot.

Y 5. A device for drawing ellipses comprising a carrier, track means onwhich the carrier may move back and forth, a fixe'd bearing, a crank pinmounted for turning about thebearing, means- OLIVER J. HOBSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 184,493 Anderson Nov. 21, 1876731,018 Carlton June 17, 1903 957,114 Shea May 3, 1910

